Stabilization of iodine in salt and other feed materials



2,144,150 PATENT OFFICE STABILIZATION 0F IODINE IN SALT AND OTHER FEED MATERIALS Edwin 1B. Hart and Walter B. Griem, Madison,

Wis., and La Verne E. Clii'corn, Chicago, 111., assignors to Wisconsin Alumni Research Foundation, Madison, Wis., a sin corporation of Wiscon- No Drawing. Application June 13, 1938, Serial No. 213,446

15 Claims.

This application is a continuation-in-part of our copending application Serial Number 747,420, filed October 8, 1934.

Iodine is an essential element for protection against common goiter or the enlargement of the thyroid gland. The most practical way to distribute iodine to man as well as beast for this purpose, is by the iodization of salt; but it is also accomplished by the iodization of other commercial dry feed and feed supplement materials, as, for example, feeding mineral mixtures, commercial limestones, feeding limes, commercial earth salts, calcium and/or magnesium carbonates. These materials all find their way into human or animal nutrition. The usual method of iodization of salt and these other materials is to associate by mixing therewith a suitable quantity of potassium iodide.

It has been found, however, that, although the salt or other material in the course of manufacture is treated with the proper amount of iodide, the iodine in the mixture becomes unstable and the mixture gradually loses its iodine content, so that by the time the product reaches the consumer it may have lost all or a greater portion of its iodine content.

Efiorts in the past to overcome this loss on the theory that if the salt or other material which is to carry the iodide is rendered alkaline by the addition of an alkaline salt, such as so-' dium carbonate, sodium bi-carbonate, magnesium carbonate, calcium carbonate, or sodium phosphate, the potassium iodide in the salt or other mixture will be stabilized, but these mixtures have not been successful, as investigation has shown.

We have discovered by extensive experiment that the loss of iodine is brought about by oxidation of the iodide which results in its conversion into free iodine in an elemental vapor stage which is readilyllberated from the salt or other material. This is evidenced by the fact that iodized salt or other feed materials contain traces of many substances, such as iron, copper and manganese in their highest state of valency,

which are in themselves strong oxidizing agents, and their presence in the mixture brings about this conversion of the iodide to free iodine. The oxygen in the air also plays an important part in the liberation of iodine by photochemical oxidation, by direct oxidation of the iodide in a slightly acid salt or other mixture, and by oxidation by ozone present in the air and originating from oxygen. These reactions occur only in the presence of moisture.

We have found that by the use of a reducing agent in the mixture of salt or other material and potassium iodide or other suitable iodine carrier, the iodine content of the mixture is rendered stable and the loss of iodine prevented. The reducing agent acts to prevent the oxidation of the potassium iodide and its conversion to free or elemental iodine.

Our invention includes the use of any reducing agent having the properties or being capable of preventing the oxidation of iodides to elemental iodine, and otherwise not deleteriously reactant with other ingredients of the mixture. Such reducing agents as sodium thiosulfate, sodium hypophosphite, sodium phosphite, starch, glucose, maleic acid, metallic iron, and calcium gluconate have all been found by test as thus effective to prevent oxidation of the iodide.

The various conditions to which iodized salt and other dry nutrition materials are subject in practice, were all taken into consideration and established in carrying out extensive tests and experiments in the determination of the effectiveness of the various reducing agents; for instance, in connection with our investigations of iodized salt, the salt was sometimes placed in bottles and stoppered, or in bags where it would be subject to free circulation of air, or exposed to sunlight, and the iodine content was determined after three to five months storage.

Following is a table showing the results of experiments conducted with various reducing agents. In these experiments the usual iodized salt was used, comprising commercial salt plus potassium iodide.

I ti 1 Starch test Analysis m a s owing a ter3 Description analysis loss of months iodine period Commercial salt+potassium iodide (KI) in bottle 0228 Positive.-. .0201 Commercial salt+potessium iodide (KI) in bag 0228 0170 Same as #1+.l 0 Fe 0221 Negative.. .0226 Same as #1+.2 a Fe+.2% Na CO 0202 Negative 0203 Same as #1+{:8;; g f- .0228 Positive .00059 Same as #73+.5% Fe .0216 Negative 0213 Same as #73+.5% NaHzPO; .0208 Negative 0221 Same as #73+.5% Na1S0;.5H;0 .0206 Negative" 0206 Same as #73+.5% Na1CO +.5% Fe .0213 Negative" 0210 Same as #73+.5% Na1C0;+.5% NaHgPO: 0215 Negative" 0210 Same as #73+.5% N8z00a+.5% Na;S1O;.5H1O 0216 Negatlve 0210 Same as #73+.5% Na1C0;+.5% starch .0216 Negative 0218 Same as #78+.5% NanC 0;+.5% glucose .0228 Negative 0214 Experiments Neal and, 2 were intended to represent the usual iodized salt mixtures compria- 7 ing commercial salt. and potassium iodide, stored inbottles or, bass for three months. and} illus-:

trate theloss oiiodine during this period. f g -.Experlrnent No.73 represents iodized salt sim-' A liar. to Nos, 1 and 2; in which {copper sulfate I (011804) and ferric chloride (FeCls) were-present in the, mixtures as; impurities. Such impurities present in traces in. commercial iodized salts. .Fi irthermore, such impurities are activein randating the iodideiunstable and hastening loss by render thesalt acid and are likely to be :tound oxidation.

I to use, in addition to the reducing agent, an agent capable of rendering the material alkaline, and

iwhere the iodized material isacid'we prefer experimentsNos. 89 to 93 illustrate. this alkaline producing salt as sodium carbonate (Na2C0:)-

inthe mixture.

' vIn experiments Nos. 171, 84 and 85', the reduc ing agents, metallic iron (Fe): andsodium-hypo phosphite' (NaHrPOz) are mixed-with the iodized salt alone and. without any alkaline-producing agent present; Theresults in these cases show 3 7 negative; that is, that the reducing; agent alone I is efiective to prevent theloss or iodine. g

I v I I I The following formulas are illustrative oi mix-1 I i tures which we have found to be efiectivein completely stabilizing thev iodide:

I i. For iodized table salt: contained in closed cartons-,the addition; of .5%-sodium carbonate plus ;.5% sodium hypophosphite.

2. For iodized salt contained inbags or 'oon--' tainers where air can circulate freely, theaddh' .tion; of .5% sodium carbonate plus .1% metallic iron in finely divided or: powdered ro'rm and flsuspendedin starch.

suitable stahilizing mixture employing the latter formula is prepared :as follows: i

-5- parts- 01' starch, 5 parts or water, 1 part of powdered metallic iron (passing mesh sieve), 14 parts of common salt are mixed together. No heat is applied in drying this mixture, but it is allowed'to stand after stirring until dry. This produces a light grey powder which will not impart ofl-color to the salt. Two grams of this mixture added to 98 grams 0! salt gives a mixture containing approximately .1% of iron. 40 pounds of the above mixture-per ton of salt will give approximately the same percentage of metallic iron in the iodized salt. For practical convenience the potassium iodide or other iodine carrier can be added to the above mixture as well as the alkaline salt so that a complete mixture of alkaline salt, iodine carrier, and reducing agent is prepared before mixing with the salt itself.

Metallic iron is not only highly effective as a stabilizer, but it is also a harmless and nondeleterient reagent and is therefore acceptable in food. Being black in color, however, it would add specks to the salt and also tend to settle out. To obscure the specks from the color standpoint, it is placed in starch which itself is a reducing agent.

Potassium iodide is referred to above as the iodine carrier because of the fact that it is practically the only iodide compound which is produced commercially for use as a source of iodine for salt and other dry feed mixtures and feed supplements. However, our tests and experiments have shown that the iodine content of any of the other iodides in the group of alkaline iodides (potassium iodide, sodium iodide, am-

I fo'n'ium: iodide, calcium iodide, and magnesium -iodide),'is;eflectively stabilizedwhen associated i with salt or other feed mixtures or feed suppoi i merits tor the purpose of iodization or these mate g 1 rials in accordance with, our invention. Tl'ie i viodides in this group lose elemental iodine in the f l presence of the impurities in these mixtures when 1 or supplements.

' In salt Initial imonth NaI-(scnii um iodide):-

Notstsbilizcd I .0195 flt-abilizedufl ns .0179 N114! (.ammoniumiodido):- Notstabiiize .0204 .0151 Stabllized- I 4013a mo CaIcclciumiodidc): I o stshilize'd v.0143 .0094 Stabilized .0161 .0100

In: these examples the same .tormula was in substantially the same proportions an her-elm- I beiore'state'd in connection with the stabilization I I oipotassium iodide, except that, instead of so dium hypophosphflte, sodium thiosulfate was used wasthereducingagent.

hereinbeiore stated, various dietary feed materl'alasuch as 'mineral'ieed mixtures, com 1 I merciallimestones, feeding I limes, commercial earthsalts, calciumand/or magnesium carbon 1 ates are used: as means i'or'distributing'iodine to: humans and animals, but in these materials,

conversion. Our extended tests and experiments show that the stabilization of the iodine content of these mixtures is accomplished by the use of a reducing agent in the mixture in the same manner as in salt. For instance, in a typical mineral feed mixture containing limestone, bone meal, bone black, super phosphates, salt, charcoal, Glaubers salt, epsom salt, sulfur, bicarbonate of soda, manganese sulfate, oxide of iron, iron sulfate, anise, and potassium iodide, the iodine content was stabilized by incorporating in the mixture sodium thiosulfate and sodium carbonate in substantially the same proportions as found to be effective for iodized commercial salt. Tests showed that the mixture not stabilized and with an initial iodine content of .0583% lost .0083% or 14.2% of the initial content in a period of about 100 days, whereas this same mixture stabilized lost none of its iodine content in the same period.

Likewise, tests 01 typical mineral mixtures conslsting of commercial limestone and potassium iodide (initial iodine content of .1395%) and sodium thiosuli'ate, showed that the mixture retained the same percentage (.1395%) of iodine content after a period of days. In these instances no added alkaline agent was necessary because the limestone itself was strongly alkaline. Substantially the same proportions 01' potassium iodide and sodium thiosulfate were used as found to be effective for iodized commercial salt.

We claim:

1. A commercial dry feed mixture in which the iodine content is stable, including mineral food ;'used as. iodine carriersiorieed or ieedimlxtu'res E '38 in. the case of salt, the iodideis converted to i i free or elemental iodine and lost',-due-to'the fact that these materials usually contain those im i 'Puritlessuch .as iron, copper and manganese, which actupon the iodide to bring about this material, an iodide of the group of alkaline iodides, and a reducing agent acting to prevent the conversion of said iodide to elemental iodine.

2. A commercial dry feed mixture in which the iodine content is stable, including mineral food material, an iodide of the group of alkaline iodides, an alkaline agent, and a reducing agent acting to prevent the conversion of said iodide to elemental iodine.

3. A commercial dry feed mixture in which the iodine content is stable, including mineral food material, potassium iodide, sodium carbonate, and sodium thiosulfate.

4. A commercial dry feed mixture in which the iodine content is stable, including mineral food material, potassium iodide, sodium carbonate, sodium thiosulfate, and starch.

5. A stabilized mineral composition including salt, an iodine of the group of alkaline iodides, an alkaline agent, and a reducing agent cooperating to maintain the iodide in a non-oxidized state.

6, A stabilized mineral mixture comprising salt, potassium iodide, an alkaline agent, starch, and a reducing agent all co-reactingto prevent the conversion of the iodide to elemental iodine.

7. A stabilized mineral composition including salt, potassium iodide, an alkaline agent, and a reducing agent cooperating to maintain the iodide in a non-oxidized state. I

8. A mineral composition including salt, potassium iodide, sodium carbonate, and a reducing agent having the property of preventing the conversion of the iodide to free iodine.

9. A mineral composition including salt, potassium iodide, sodium carbonate, starch, and an anti-oxidant having the property of preventing the conversion of the iodide to free iodine.

10. A stable mineral composition in which potassium iodide is maintained against conversion to iodine, including salt, potassium iodide, sodium carbonate, and sodium thiosulfate.

11. A stable mineral composition in which potassium iodide is maintained against conversion to iodine, including salt, potassium iodide, sodium carbonate, sodium thiosulfate, and starch.

12. A stable mineral composition in which potassium iodide is maintained against conversion to iodine, including salt, potassium iodide, an alkaline agent, and sodium thiosulfate.

13. A commercial dry feed mixture in which the iodine content is stable, including commercial limestone, an iodide of the group of alkaline iodides, and a reducing agent acting to prevent the conversion of said iodide to elemental iodine.

14. A commercial dry feed mixture in which the iodine content is stable, including commercial limestone, potassium iodide, and sodium thiosulfate.

15. A commercial dry feed mixture in which the iodine content is stable, including commercial limestone, potassium iodide, sodium carbonate, and sodium thiosulfate.

EDWIN B. HART. WALTER B. GRIELL LA VERNE E. CLIFCORN,

CERTIFICATE OF CORRECTION.

Patent No 2,ll 4.,15O.

January 17 95 9 EDWIN B. HART, ET AL,

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correctionas follows: Page5 first column, line 19, claim 5, for the word "iodine" read iodideyand that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 21st day of March, A.D. 1939.

(Seal) Henry Van Arsdale'.

Acting Commissioner of Patents. 

